FIG. 1 depicts a wireless communication system 10 in accordance with the prior art. Wireless communication systems 10 comprises a base station 12, a digital cellular switch (DCS) 14, and a plurality of mobile-telephones 16 and 18 associated with users. Base station 12 utilizes resources, such as radio frequency (RF) bandwidth, channel element (CE) resources, Walsh codes and packet pipe (PP) bandwidth, to support fundamental channels (FCH) and supplemental channels (SCH) in the forward direction over which data may be transmitted to mobile-telephones 16 and 18. Base station 12 typically having sufficient resources to support multiple FCHs and SCHs. The resources supporting a particular FCH, also referred to herein as fundamental channel or FCH resources, are dedicated to the mobile-telephone to which base station 12 is in communication over that FCH. By contrast, the resources supporting a particular SCH, also referred to herein as supplemental channel or SCH resources, may also be supporting other SCHs, but not concurrently. Typically, SCH resources are all remaining resources belonging to base station 12 which are not supporting FCHs, i.e., all resources minus FCH resources. Some or all SCH resources may be used to support a SCH depending on the needs associated with the user of the SCH.
In the prior art, data is transmitted either over the FCH or SCH depending on the amount of data to be transmitted and availability of SCH resources. Specifically, if the amount of data for a user exceeds a data threshold and SCH resources are currently available to support a SCH for that user, the data is transmitted over a SCH, wherein the data threshold, for example, is an amount exceeding a data transmission capacity associated with the FCH of the user. Otherwise, the data is transmitted over the FCH associated with the user. Note that the manner in which a determination is made regarding whether there are sufficient SCH resources currently available to support a SCH for a particular user depends on factors such as maximum data rate of user, data backlog for user, available CE, RF, Walsh codes and PP resources, as is well-known in the art.
Data to be transmitted to mobile-telephones 16 and/or 18 is received by DCS 14 and subsequently routed to base station 12 for transmission to mobile-telephone 16 and/or 18. The following routing protocol is used for routing data from DCS 14 to base station 12. If the data to be transmitted does not exceed the data threshold, DCS 14 routes the data to base station 12 for transmission over the FCH of the user to which the data is intended. If the amount of data to be transmitted to a particular mobile-telephone exceeds the data threshold, DCS 14 checks for current SCH resource availability by issuing a data notify request (DNR) to base station 12, wherein the data notify request indicates a resource request for a SCH and the amount of data to be transmitted.
Upon receipt of the data notify request, base station 12 determines whether it has SCH resources currently available to support a SCH for that user. If base station 12 determines it currently has such SCH resources available, base station 12 assigns the currently available SCH resources to the user, sets up a SCH utilizing the currently available SCH resources, and responds with an approval indicating when DCS 14 should begin routing the data to base station 12, i.e., after the SCH has been set up. Upon receipt of the approval, DCS 14 begins routing the data to base station 12 at the time indicated in the approval for transmission over the SCH.
If base station 12 determines there are no currently available SCH resources to support a SCH for the user, base station 12 responds with a denial indicating to DCS 14 not to route the data to base station 12. Upon receipt of the denial, DCS 14 delays a waiting period or predetermined time interval, e.g., half a second, before issuing another data notify request if, at the end of waiting period, DCS 14 still has data for the same user over the data threshold. Note that during the waiting period, DCS 14 may be routing all or some of the it has for the user for transmission over the FCH of the user. Thus, it is possible that at the end of the waiting period, DCS 14 may not have data for the user over the data threshold.
The above described routing protocol can cause overhead delays which, in turn, result in gaps between data bursts. FIG. 2 depicts a time chart 20 illustrating, for example, shared SCH resources 21 supporting one SCH at a time. During time intervals t0 to t1 and t4 to t5, SCH resources 21 are supporting a SCH for mobile-telephone 16 over which data bursts 22 and 26 are being transmitted. Similarly, during time interval t2 to t3, SCH resources 21 are supporting a SCH for mobile-telephone 18 over which data burst 24 is being transmitted. During time intervals t1 to t2 and t3 to t4, gaps 28 and 30 exist during which SCH resources 21 are not utilized.
Gaps 28 and 30 may be caused by overhead delays associated with the routing protocol, among other reasons. For example, suppose DCS 14 has data for mobile-telephone 18 which exceeds the data threshold. At time t6, DCS 14 issues a data notify request for mobile-telephone 18. At this time, base station 12 is utilizing SCH resources 21 to support a SCH for mobile-station 16 in the transmission of data burst 22 and does not currently have any other SCH resources available to support a SCH for mobile-telephone 18. Accordingly, base station 12 responds to DCS 14 with a denial of the data notify request. DCS 14 waits the duration of the waiting period, i.e., t6 to t7. At the end of the waiting period, DCS 14 still has data for mobile-telephone 18 which exceeds the data threshold. Accordingly, at time t7, DCS 14 issues a data notify request for mobile-telephone 18. At this time, SCH resources 21 are now available and can be used to support a SCH for mobile-telephone 18. Thus, base station 12 assigns SCH resources 21 to mobile-telephone 18, sets up a SCH using SCH resources 21 and responds with an approval for DCS 14 to begin routing the data to base station 12 at time t2, wherein the time period between times t7 and t2 corresponds to a time period for setting up the SCH for mobile-telephone 18.
In this example, time periods t1 to t7 and t7 to t2 are caused by overhead delays, and collectively form gap 28. The time period t1 to t7 being caused by DCS 14 delaying the waiting period, and the time period t7 to t2 being caused by the setting up of the SCH for mobile-telephone 18 using SCH resources 21. Gaps resulting from overhead delays are undesirable because they result in the inefficient utilization of SCH resources. Accordingly, there exists a need for a more efficient utilization of SCH resources.